1. Field of the Invention
The present invention relates to a liquid-discharging recording head in which liquid channels or discharging ports are formed, for example, in a resin top plate according to grooving, drilling or the like by laser irradiation, a method and apparatus for manufacturing the same, a head cartridge, and a liquid-discharging recording apparatus.
2. Description of the Related Art
In general, a liquid-discharging recording head for performing recording or printing on a recording medium (recording paper or the like) by discharging a recording liquid (ink) from fine discharging ports (orifices) in the form of flying droplets includes a substrate (heater board) having a plurality of electrothermal transducers and lead electrodes thereof provided thereon. A resin nozzle layer (liquid-channel forming layer) for forming liquid channels (nozzles) and a common liquid chamber is laminated on the substrate, and a glass top plate having recording-liquid supply tubes provided therein is superposed on the resin nozzle layer. Recently, liquid-discharging recording heads, in which the above-described glass top plate is omitted, a resin top plate is integrally formed according to injection molding or the like by providing recording-liquid supply tubes and the like so as to be integrated with liquid channels and a common liquid chamber, discharging ports are then formed therein, and the top plate is pressed against the substrate by a spring member so as to be integrated therewith, have been developed. In such liquid-discharging recording heads, the number of assembling components is greatly reduced, and the assembling process is greatly simplified. As a result, it is expected that the cost of such a liquid-discharging recording apparatus can be greatly reduced.
FIG. 1 is a schematic partially-broken perspective view illustrating the basic configuration of a liquid-discharging recording head Eo using a resin top plate which is formed in the above-described manner. In FIG. 1, the liquid-discharging recording head Eo indicated by partially breaking the resin top plate includes a substrate 101 having a plurality of electrothermal transducers 101a, serving as discharging-energy generating elements for generating thermal energy as energy utilized for discharging a liquid, provided thereon, and a resin top plate 102 having liquid channels 102f provided on corresponding ones of the electrothermal transducers 101a, and a common liquid chamber 102c. A discharging-port plate portion 102b having discharging ports (orifices) 102g communicating with corresponding ones of the liquid channels 102f, and a cylindrical projection 102d having a liquid supply port 102e opened to the common liquid chamber 102c are integrally provided.
The resin top plate 102 having the liquid channels 102f, the common liquid chamber 102c, the dicharging-port plate portion 102b and the cylindrical projection 102d is integrally formed according to injection molding, and then, the discharging ports 102g are formed. After positioning the resin top plate 102 so that the liquid channels 102f are positioned above corresponding ones of the electrothermal transducers 101a on the substrate 101, the top plate 102 is pressed against the substrate 101 by an elastic member (not shown) so as to be integrated with the substrate 101. The substrate 101 is fixed on a base plate 104 together with a circuit substrate 103 mounting a driving circuit for generating an electric signal to each of the electrothermal transducers 101a, according to a known method, such as screwing or the like.
A method for manufacturing the resin top plate 102 has also been developed in which after integrally forming a blank (primary molding), comprising a main-body portion 102a before providing the liquid channels 102f, the discharging port plate 102b before providing the discharging ports 102g, and the like, according to injection molding, the liquid channels 102f are formed in the main-body portion 102a of the resin top plate 102 using excimer laser, and the discharging ports 102g are also formed in the discharging-port plate 102b using excimer laser.
Since the resin top plate can be inexpensively manufactured by combining injection molding and laser processing, the cost of the liquid-discharging recording head can be further reduced. An excimer laser apparatus is suitable as a laser processing apparatus for grooving and drilling a blank obtained by injection molding by projecting a laser beam. Such an excimer laser apparatus generally includes a laser oscillator serving as a laser light source, a mask having an aperture pattern for forming liquid channels and discharging ports of a liquid-discharging recording head, and an optical system for projecting the aperture pattern of the mask using a laser beam.
When forming grooves, serving as liquid channels of a liquid-discharging recording head, and forming holes, serving as discharging ports of the head, it is necessary to perform such processing by projecting a laser beam having a high energy density per unit time, in order to obtain grooves and holes having good shapes, obtain large discharging ports, and shorten times required for forming the grooves and holes. In general, as the energy density per unit time of the projected laser beam is larger, the cone angle in processing by the laser beam is smaller, so that accuracy is improved, and grooves and holes having good shapes can be obtained. Particularly when forming holes serving as discharging ports, the cone angle in processing is reduced by projecting a laser beam having a high energy density per unit time, so that large threaded discharging ports can be obtained.
As the energy density per unit time of the projected laser beam is larger, the processing speed by the laser beam is higher. Hence, processing by a laser beam having a high energy density per unit time has many advantages such that grooves and holes can be formed in a short time.
However, when forming grooves, serving as liquid channels, and holes, serving as liquid discharging ports, using a laser beam having a high energy density per unit time as in the above-described conventional technique, if a laser beam having a high energy density per unit time exceeding a threshold is projected onto a resin, the resin tends to be deformed due to instantaneous energy concentration, thereby causing deviation in the dimensions or the pitch of formed grooves and holes, and generation of burrs around threaded discharging ports.
FIG. 2 is a schematic cross-sectional view illustrating a result of conventional laser processing.
In FIG. 2, there are shown a material to be processed 300, a through hole 303, and a laser beam 304. As laser ablation processing is performed for the material 300, a sheet-like lid 301 is formed on the surface of the material 300 immediately before the through hole 303 is threaded. By further projecting the laser beam 304 from this state, the lid 301 is further processed to provide a state in which the through hole 303 is threaded. If the processing by the laser beam 304 is performed within the through hole 303 at a constant speed, the lid 301 is projected directly in the direction of the processing. However, if variations are present in the processing speed of the laser beam 304 within the through hole 303, a portion where the processing speed is low operates as a hinge portion 302, and the lid 301 is opened as a door is opened. The hinge portion 302 is torn due to a shock when the lid 302 has been moved, to produce barrs at the torn portion.
When deviation in the dimensions and the pitch of the grooves occurs, misalignment between the grooves and the electrothermal transducers occurs when the top plate is pressed against the substrate (heater board) having the electrothermal transducers in order to be integrated therewith. This misalignment will cause a decrease in the efficiency of conversion from thermal energy to kinetic energy for generating bubbles in the liquid and discharging liquid droplets. If burrs are produced around the threaded discharging ports, discharge of the liquid may be insufficiently performed, for example, by making the direction of discharge of the liquid unstable, or generating unnecessary liquid droplets. If deviation in the pitch of the formed holes occurs, the pitch of the holes deviates from the pitch of the grooves serving as the liquid channels. Hence, it is impossible to obtain discharging ports having a desired size. A liquid-discharging recording head having such problems will have insufficient functions as a product.
If the above-described processing is performed by reducing the energy density per unit time of the projected laser beam, the above-described problems will not occur. However, since the cone angle by the processing increases, it is difficult to produce deep grooves and to obtain large discharging ports, and a long time will be required for the processing, thereby causing, for example, an increase in the cost of the processing required for manufacturing the head.
Accordingly, at present, it is necessary to strictly control and appropriately adjust the energy density per unit time of the projected laser beam in order to prevent occurrence of burrs when the liquid-discharging recording head is manufactured. It is also indispensable to check the shapes of the grooves and the holes, and the presence of burrs around the discharging ports in the process of manufacturing the recording head, thereby causing a great decrease in operational efficiency in the manufacture of the liquid-discharging recording head.
The present invention has been made in consideration of the above-described problems.
It is an object of the present invention to provide a method and apparatus for manufacturing a liquid-discharging recording head capable of preventing deviation in the dimensions and the pitch of grooves, serving as liquid channels, and holes, serving as discharging ports, and generation of burrs around the discharging ports while maintaining the grooves and the holes to desired sizes and without increasing a time required for the processing when processing the grooves and the holes by projecting a laser beam, and to provide a liquid-discharging recording head having excellent printing characteristics manufactured by such a method, and a head cartridge and a liquid-discharging recording apparatus having such a head.
According to one aspect, the present invention relates to a method for manufacturing a liquid-discharging recording head by projecting a laser beam onto a substance to be processed, and forming holes serving as discharging ports for discharging a liquid. The method includes the step of processing the substance by changing an energy density per unit time of the laser beam projected onto the substance.
According to another aspect, the present invention relates to an apparatus for manufacturing a liquid-discharging recording head. The apparatus includes a light source for generating a laser beam, holding means for holding a substance to be processed in which holes serving as discharging ports for discharging a liquid are formed by the laser beam, and an optical system, including a mask, positioned between the light source and the holding means. The sustance is processed by changing an energy density per unit time of the laser beam projected onto the substance.
In the method for manufacturing a liquid-discharging recording head according to the present invention, a laser beam is used as a light source, a mask is used, the image of the mask is projected onto a primary molding, serving as a substance to be processed, using an optical system, and grooves, serving as liquid channels, and holes, serving as discharging ports, are subjected to ablation processing. The substance is processed by changing the energy density per unit time of the laser beam projected onto the substance.
In the manufacturing method of the present invention, it is desirable that the substance is processed by changing the energy density per unit time of the laser beam projected onto the substance continuously or stepwise.
In the manufacturing method of the present invention, the energy density per unit time of the laser beam projected onto the substance may be changed by adjusting the oscillation voltage or the oscillation frequency of the laser beam, or by simultaneously adjusting the oscillation voltage and the oscillation frequency of the laser beam.
In the manufacturing method of the present invention, it is also possible to change the energy density per unit time of the laser beam projected onto the substance by attenuating the laser beam using a component other than a laser mask, or by moving the substance.
In the manufacturing method of the present invention, when performing ablation processing of the substance by projecting the laser beam thereon, the energy density per unit time of the laser beam projected onto the substance is changed by dividing the laser beam. Thus, deviation in the dimensions and the pitch of the grooves and the holes due to distortion of resin is prevented, and the generation of burrs around the discharging ports threaded by the laser beam is prevented, while maintaining the depth of the grooves and the size of the discharging ports to desired shapes and without increasing processing time.
When performing ablation processing of the substance, by continuously changing the energy density per unit time of the laser beam projected onto the substance, it is possible to continuously change the shape of the processed portion in accordance with the change of the energy density, and prevent a change in the shape of the processed portion which is inevitable as a result of an abrupt change in the energy density per unit time of the laser beam, and prevent deviation in the dimensions and the pitch of the formed grooves and holes. In another approach, by changing the energy density per unit time of the laser beam stepwise, deviation in the dimensions and the pitch of the grooves and the holes due to deformation of resin is prevented. After projecting a few pulses of a laser beam having a low energy density per unit time immediately before completion of the processing after projecting a laser beam having a high energy density per unit time, it is possible to prevent generation of burrs around the discharging ports.
It is possible to change the energy density per unit time of the laser beam projected onto the substancematerial by adjusting the oscillation voltage of the laser beam, adjusting the oscillation frequency of the laser beam, simultaneously adjusting the oscillation voltage and the oscillation frequency of the laser beam, attenuating the laser beam using a component other than the laser mask, or moving the substance.
According to the present invention, when forming liquid channels and discharging ports in a resin top plate or the like by forming grooves and holes by projecting a laser beam, by changing the energy density per unit time of the laser beam continuously or stepwise, a change in the shape of the processed portion which is inevitable as a result of an abrupt change in the energy density is prevented, and deviation in the dimensions and the pitch of the formed grooves and holes, and generation of burrs around the threaded discharging ports are prevented. In addition, it is possible to accurately form grooves, serving as liquid channels, having a desired depth, and discharging ports having a desired size, and to form the liquid channels and the discharging ports in a short time. As a result, it is possible to improve productivity and reduce the production cost.
In a liquid-discharging recording head manufactured by changing the energy density per unit time of a laser beam when forming liquid channels and discharging ports in a resin top plate or the like by forming grooves and holes by projecting the laser beam, deviation in the dimensions and the pitch of the formed grooves and holes, and generation of burrs around the threaded discharging ports are prevented, and it is possible to accurately form grooves, serving as liquid channels, having a desired depth, and discharging ports having a desired size. Since misalignment between the liquid channels and the discharging ports, and electrothermal transducers does not occur, an excellent printing property can be obtained.